Advance care planning (ACP) refers to discussions or written directives about preferences for life-sustaining treatment and surrogate decision makers, and it has been promoted to preserve individuals' autonomy in health care decisions at the end of life (EOL). Although the adoption of documented ACP has increased, solely increasing written directives may not influence health care if not accompanied by ongoing patient-clinician discussions; yet little is known regarding factors associated with having such ongoing discussions. Moreover, there is a growing appreciation that ACP should be highly individualized and informed by the likely course from diagnosis to death (e.g., cancers may progress slowly compared to some other conditions); however, little is known about ACP and its role in influencing health care across different diseases. Also, most studies of ACP and health care utilization (HCU) have focused on institutionalized populations or on decedents, which limits the applicability to the larger aging population, most of whom live with chronic disease. To address these major gaps, we propose to leverage the wealth of self-reported prospective data from the Nurses' Health Study, an ongoing cohort of female nurses initiated in 1976 (n=60,000 currently aged 68-93 years) for whom we are linking participant data and Medicare claims data. For participants, reported ACP status is available and will be updated over time, including written directives and ongoing ACP discussions with a physician. Our first Aim is to: 1a) assess determinants of ACP completion, both with and without ongoing physician discussions; 1b) among those with written ACP and no discussions, identify predictors of new discussions over 4 years of follow-up; and among those with no ACP, identify predictors of ACP completion; 1c) explore if determinants and predictors of ACP differ by major disease groups (i.e., neurodegenerative disease, heart/respiratory disease, cancer). Second, we propose to: 2a) among decedents, evaluate the relationship of ACP and EOL HCU and explore whether this relationship differs across different causes of mortality (i.e., cancer, heart/respiratory disease r neurodegenerative disease); 2b) among all participants, evaluate the relationship between ACP status and overall HCU. In a new secondary Aim, we will begin to collect and examine participants' specific preferences for aggressive treatment at the EOL. Overall, the proposed research is innovative in representing a substantive departure from existing studies by shifting the focus to ACP as an ongoing discussion with a physician, examining a community-dwelling population and considering ACP within specific disease groups. The contribution of the proposed work will be significant in providing data to help health care providers improve and target approaches to promote timely and effective ACP and to help inform ACP policies for community-dwelling persons. Importantly, the proposed R21 will serve to establish the foundation required to initiate extensive future longitudinal research on ACP and patient-centered HCU.